Deformation trend prediction method for deep foundation pit based on multimodal sensing data

Abstract

The present invention relates to the field of construction monitoring technology, and in particular to a method for predicting deformation trends of deep foundation pits based on multimodal sensing data. The method comprises calculating pore water pressure differentials and predicted settlement rates to determine ground settlement conditions, detecting the actual horizontal displacement of diaphragm guide walls, and drawing a displacement curve of the diaphragm walls; determining the support conditions of internal supports based on curve diagnostic conditions, estimating the total horizontal displacement of several guide wall levels after support removal, or inspecting the loads acting on the internal supports in corresponding areas; calculating load loss to determine the reason why the horizontal displacement does not meet the curve diagnostic conditions; calculating the total horizontal displacement of the diaphragm guide walls at several guide wall levels after support removal, calculating a deformation evaluation value to determine the deformation trend of the foundation pit; and adjusting the displacement increment of the next guide wall level based on a comparison between the estimated total horizontal displacement and the actual horizontal displacement detected. The present invention determines the deformation trend of the foundation pit by calculating the deformation evaluation value of the deep foundation pit.

Description

Technical Field

[0001] The present invention relates to the technical field of construction monitoring, and in particular to a method for predicting deformation trends of deep foundation pits based on multimodal sensing data. Background Art

[0002] Deep foundation pit excavation in urban areas can cause deformation of the soil in and around the excavation area. Excessive deformation will cause damage to adjacent buildings and infrastructure. To limit deformation, a lateral displacement limit of the wall is usually set as a certain proportion of the excavation depth, and deformation monitoring is used to analyze and evaluate the deformation of the wall. When the monitoring data is less than the set limit, the deformation of the structure is within a relatively safe range. Otherwise, the structure will be in an unfavorable state. This evaluation method can directly reflect the current condition of the foundation pit and provide decision makers with real-time monitoring information.

[0003] Chinese Patent Publication No.: CN118292498A discloses a real-time monitoring and early warning method and system for deformation of steel sheet piles in deep foundation pits. The method includes: real-time reconstruction of a three-dimensional real-scene model of a deep foundation pit based on drone aerial photography and oblique photogrammetry technology; using a multi-scale model to model point cloud comparison algorithm (Multiscale Model to The Model Cloud Comparison (M3C2) algorithm compares the distance changes of the deep foundation pit point cloud model at different times to obtain a deep foundation pit deformation cloud map. Based on the deformation cloud map, the deformation amount and deformation rate of the steel sheet piles are measured, and the deformation trend of the steel sheet piles is predicted, thereby achieving real-time monitoring and alarming of the deformation of the deep foundation pit steel sheet piles, which has the effect of improving the quality of construction monitoring and project management. It can be seen that the real-time monitoring and early warning method and system for the deformation of deep foundation pit steel sheet piles have the following problems:

[0004] The deep foundation pit excavation construction includes the process of setting up internal supports. Only the deformation of steel sheet piles is monitored without eliminating the axial support effect of the internal supports on the deep foundation pit, resulting in inaccurate deformation prediction. Summary of the Invention

[0005] To this end, the present invention provides a deep foundation pit deformation trend prediction method based on multimodal sensing data to overcome the problem in the prior art of inaccurate deformation prediction, which only monitors the deformation of steel sheet piles without eliminating the axial support effect of internal supports on the deep foundation pit.

[0006] To achieve the above objectives, the present invention provides a method for predicting deformation trends of deep foundation pits based on multimodal sensing data, comprising:

[0007] Detect the actual pore water pressure according to the initial detection cycle, calculate the pore water pressure difference and predict the settlement rate to determine the formation settlement status;

[0008] Determining to continue monitoring the ground settlement state or detecting the actual horizontal displacement of the diaphragm wall guide wall according to the ground settlement state, calculating the actual horizontal displacement based on the measured horizontal displacement, and drawing a displacement curve of the diaphragm wall guide wall;

[0009] Determine the support condition of the internal support according to the curve diagnosis condition of the displacement curve, estimate the total horizontal displacement of the diaphragm wall guide wall at several guide wall levels after the support is removed, or check the load acting on the internal support in the corresponding area;

[0010] Check the loads acting on the internal supports and ground-connected walls to calculate the load loss and determine whether the reason why the horizontal displacement does not meet the curve diagnosis conditions is due to internal support load loss;

[0011] Calculate the total horizontal displacement of the diaphragm guide wall at several guide wall levels after the support is removed based on the estimated displacement increment after support removal, calculate the deformation evaluation value based on the total horizontal displacement and the current excavation depth, and determine the foundation pit deformation trend and support removal sequence;

[0012] Remove the internal supports at different guide wall levels according to the determined support removal sequence, and adjust the displacement increment of the next guide wall level based on the comparison result between the estimated total horizontal displacement and the actual horizontal displacement detected;

[0013] The guide wall level is a hierarchical division of the ground-anchored wall guide wall according to the depth of the surrounding soil where the ground-anchored wall guide wall is located.

[0014] Furthermore, the process of determining the subsidence state of the formation includes,

[0015] Detect the actual pore water pressure according to the initial detection cycle, calculate the pore water pressure difference between the actual pore water pressure detected in the current initial detection cycle and the historical pore water pressure detected in the previous initial detection cycle, and calculate the predicted settlement rate of the soil around the foundation pit;

[0016] If the pore water pressure difference is less than the standard water pressure difference, and the predicted settlement rate is less than the standard settlement rate, the deep foundation pit is judged to be in the first settlement state, and the actual horizontal displacement of the diaphragm wall guide wall is detected;

[0017] If the pore water pressure difference is greater than or equal to the standard water pressure difference, or the predicted settlement rate is greater than or equal to the standard settlement rate, the deep foundation pit is judged to be in the second settlement state and the ground settlement state continues to be monitored.

[0018] Furthermore, the process of drawing the displacement curve of the diaphragm wall guide wall includes:

[0019] The actual horizontal displacement is calculated based on the measured horizontal displacement, temperature difference, and measurement section length, and the displacement curve of the ground-connected wall guide wall is drawn. The displacement curve is divided into the wall top area, the excavation surface area, and the wall bottom area, and the horizontal displacement of the displacement curve in the corresponding area is obtained;

[0020] If all horizontal displacements in the corresponding area meet the curve diagnosis conditions, the internal support is judged to be normal, and the total horizontal displacement of the diaphragm wall and guide wall after the support is removed is estimated;

[0021] If any horizontal displacement in the corresponding area does not meet the curve diagnosis conditions, it is judged that the internal support of the corresponding area is loose, and the load acting on the internal support of the corresponding area is checked.

[0022] Furthermore, the determination of not meeting the curve diagnosis condition is:

[0023] If the horizontal displacement of the wall top is greater than 0.2% of the excavation depth, the support system is judged to have failed and the wall top area does not meet the curve diagnosis conditions;

[0024] If the maximum displacement of the excavation surface is greater than 0.15% of the excavation depth, the wall bending moment is judged to be excessive and the excavation surface area does not meet the curve diagnosis conditions;

[0025] If the wall bottom displacement increment is greater than the standard displacement for three consecutive days, it is judged that the base is uplifted and the wall bottom area does not meet the curve diagnosis conditions.

[0026] Furthermore, the process of checking the load acting on the internal supports of the corresponding area includes,

[0027] The load acting on the internal support is detected by an axial force meter, and the load acting on the guide wall of the ground-connected wall is detected by a concrete stress meter, and the load loss generated during the conversion process between the two is calculated;

[0028] Before the internal support removal stage, if the load loss is greater than 30% of the applied load, it is judged that the reason why the horizontal displacement does not meet the curve diagnosis conditions is the loss of internal support load, and compensation measures are taken for the internal support.

[0029] Furthermore, the process of estimating the total horizontal displacement of the diaphragm wall and guide wall after the support is removed includes:

[0030] The displacement increment after the support is removed is estimated, and the total horizontal displacement is equal to the sum of the displacement increment after the support is removed and the initial displacement before the support is removed. The deformation evaluation value is calculated based on the estimated total horizontal displacement and the current excavation depth.

[0031] Furthermore, when the deformation evaluation value is less than or equal to the first-level evaluation value, the deformation trend of the foundation pit is judged to be normal;

[0032] When the deformation evaluation value is greater than the first-level evaluation value and less than the second-level evaluation value, it is judged that there is a risk in the deformation trend of the foundation pit;

[0033] When the deformation evaluation value is greater than or equal to the secondary evaluation value, it is judged that the deformation trend of the foundation pit exceeds the safety range.

[0034] Furthermore, when the deformation trend of the foundation pit is normal, conventional construction is carried out and the internal supports are removed in a bottom-up manner;

[0035] When there is a risk of foundation pit deformation, shorten the initial inspection period and adjust the internal support removal steps;

[0036] Stop construction when the deformation trend of the foundation pit exceeds the safe range.

[0037] Furthermore, the internal supports at different guide wall levels are removed according to the determined support removal sequence, and the actual horizontal displacement of the diaphragm guide wall after the internal supports at the current guide wall level are detected in real time. The estimated total horizontal displacement is compared with the actual horizontal displacement detected.

[0038] If the difference between the estimated total horizontal displacement of the current support removal layer and the actual horizontal displacement detected is less than the difference evaluation value, the estimated result is judged to be within the normal range, and the support removal is continued according to the determined support removal order;

[0039] If the difference between the estimated total horizontal displacement of the current support removal layer and the actual detected horizontal displacement is greater than or equal to the difference evaluation value, the estimated result is judged to be out of the normal range, and the predicted displacement increment of the guide wall layer in the next support removal sequence is adjusted.

[0040] Furthermore, the process of adjusting the displacement increment includes,

[0041] When the estimated total horizontal displacement is less than or greater than the actual detected horizontal displacement, the displacement increment predicted after the support removal at the guide wall level of the internal support in the next support removal sequence is reduced or increased according to the ratio of the displacement difference and the difference evaluation value.

[0042] Compared with the existing technology, the beneficial effect of the present invention is that the stratum settlement is related to the deformation of the retaining wall and the pore water pressure. It is inaccurate to judge the foundation pit settlement by only using a single data pore water pressure difference. The pore water pressure is affected by the groundwater level distribution and other factors. At the same time, due to the long settlement observation period, this method predicts the foundation pit settlement rate through soil sensitivity, water pressure drop rate and time attenuation effect. According to the pore water pressure difference and the predicted settlement rate, it reflects whether the settlement state of the deep foundation pit is stable, and takes different treatment measures accordingly to improve the stability of the deformation trend prediction of the deep foundation pit.

[0043] Furthermore, due to the thermal expansion characteristics of the concrete constituting the guide wall of the ground-connected wall, the horizontal displacement of the guide wall at different depths is affected by temperature. After detecting the horizontal displacement, this method eliminates the influence of the thermal expansion of concrete on the measured value of the horizontal displacement of the guide wall of the ground-connected wall by calculating the actual horizontal displacement, thereby improving the measurement accuracy of the horizontal displacement of the guide wall of the ground-connected wall; and according to the displacement characteristics of the guide wall, corresponding evaluation criteria are set in different areas of the guide wall, and the displacement curve is diagnosed by the evaluation of the horizontal displacement in the corresponding area to judge whether it meets the curve diagnosis conditions and determine the support situation of the internal support. According to the support situation of the internal support, it is decided to estimate the horizontal displacement of the guide wall of the ground-connected wall after the support is removed or to check the load of the internal support in the corresponding area, thereby improving the adaptability and flexibility of deformation trend prediction for deep foundation pits.

[0044] Furthermore, due to reasons such as installation gap loss, deformation coordination loss, prestress relaxation and temperature reduction, the load acting on the inner support applied to the guide wall of the ground-connected wall has load loss. When the load loss exceeds the preset allowable loss rate, this method determines that the reason why the horizontal displacement does not meet the curve diagnosis conditions is the internal support load loss. Compensation measures are adopted for the internal support to prevent the internal support from being unable to provide load support to the guide wall of the ground-connected wall normally due to load loss, resulting in continuous horizontal displacement of the guide wall, causing deformation of the deep foundation pit or aggravating the deformation trend of the deep foundation pit, thereby affecting the accuracy of subsequent prediction of the deformation trend of the deep foundation pit.

[0045] Furthermore, before the internal supports of the deep foundation pit are removed, the method estimates the total horizontal displacement of the ground-connected wall and the guide wall after the internal supports are removed, when the deep foundation pit is in the first settlement state and the horizontal displacements in the corresponding areas all meet the curve diagnosis conditions, thereby eliminating influencing factors and increasing the accuracy of the estimation of the total horizontal displacement; the deformation evaluation value of the deep foundation pit is calculated according to the total horizontal displacement and the current depth, and the deformation trend of the foundation pit is discovered in time through real-time monitoring and calculation of the deformation evaluation value, and corresponding measures are taken to avoid instability of the foundation pit or damage to surrounding buildings due to excessive deformation, thereby providing a scientific and effective deformation assessment method for deep foundation pit construction, which is helpful to improve construction safety, optimize construction progress, reduce construction costs, improve construction efficiency and ensure the safety of the surrounding environment.

[0046] Furthermore, during the calculation process, the guide wall of the ground-connected wall is simplified to a vertically placed beam. However, in practice, the width of the guide wall of the ground-connected wall is relatively large. Therefore, there is a certain difference between the estimated total horizontal displacement calculated theoretically and the actual measured value. This method compares the estimated total horizontal displacement with the actual horizontal displacement detected, and adjusts the displacement increment after the removal of the support at the guide wall level where the internal support in the next support removal sequence is located according to the comparison result. This improves the estimation accuracy of the estimated total horizontal displacement at different guide wall levels in the deep foundation pit deformation trend prediction, and avoids the deformation of the guide wall causing ground displacement or affecting the safety of the foundation pit construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Flowchart of the steps of a method for predicting deformation trend of a deep foundation pit based on multimodal sensing data in an embodiment of the present invention;

[0048] Figure 2 Schematic diagram of the arrangement of the inner diaphragm wall, guide wall and inner support in the deep foundation pit according to an embodiment of the present invention;

[0049] Figure 3 Schematic diagram of displacement increment calculation in an embodiment of the present invention;

[0050] Figure 4 Schematic diagram of determining the deformation trend of a foundation pit according to a deformation evaluation value in an embodiment of the present invention;

[0051] In the figure: 1-ground-connected wall guide wall, 2-internal support. DETAILED DESCRIPTION

[0052] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0053] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0054] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0055] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0056] See also Figure 1-Figure 4 As shown, Figure 1 Flowchart of the steps of a method for predicting deformation trend of a deep foundation pit based on multimodal sensing data in an embodiment of the present invention; Figure 2 Schematic diagram of the arrangement of the inner diaphragm wall, guide wall and inner support in the deep foundation pit according to an embodiment of the present invention; Figure 3 Schematic diagram of displacement increment calculation in an embodiment of the present invention; Figure 4 Schematic diagram of determining the deformation trend of a foundation pit based on a deformation evaluation value in an embodiment of the present invention.

[0057] in, Figure 2 Where h is the excavation depth.

[0058] The present invention provides a method for predicting deformation trends of deep foundation pits based on multimodal sensing data, comprising:

[0059] Step S1, constructing a monitoring device for wall deformation, mechanical response, and environmental factors;

[0060] Step S2, detecting the actual pore water pressure according to the initial detection period, calculating the pore water pressure difference and predicting the settlement rate to determine the formation settlement state;

[0061] Step S3, determining to continue monitoring the ground settlement state or detecting the actual horizontal displacement of the ground diaphragm guide wall 1 according to the ground settlement state, calculating the actual horizontal displacement based on the measured horizontal displacement, and drawing a displacement curve of the ground diaphragm wall;

[0062] Step S4, determining the support condition of the inner support 2 according to the curve diagnosis condition of the displacement curve, estimating the total horizontal displacement of the diaphragm guide wall 1 at several guide wall levels after the support is removed, or checking the load acting on the inner support in the corresponding area;

[0063] Step S5: Detect the loads acting on the inner support 2 and the ground-connected wall guide wall 1 to calculate the load loss, and determine whether the reason why the horizontal displacement does not meet the curve diagnosis conditions is the loss of the inner support load;

[0064] Step S6, calculating the total horizontal displacement of the guide wall 1 of the diaphragm wall at several guide wall levels after the support is removed based on the estimated displacement increment after the support is removed, calculating the deformation evaluation value based on the total horizontal displacement and the current excavation depth, and determining the foundation pit deformation trend and support removal sequence;

[0065] Step S7: remove the internal supports at different guide wall levels according to the determined support removal order, and adjust the displacement increment of the next guide wall level according to the comparison result between the estimated total horizontal displacement and the actual horizontal displacement detected.

[0066] Deep foundation pit deformation refers to the displacement and settlement of the supporting structure and surrounding soil during the excavation process of the foundation pit, which mainly includes horizontal displacement, vertical settlement, tilt deformation and other forms.

[0067] In this embodiment, the deep foundation pit is provided with a ground-connected guide wall, the deep foundation pit adopts a layered excavation construction method, and a number of internal supports are provided inside the deep foundation pit;

[0068] Observe the layered settlement of foundation soil, and divide the deep foundation pit's diaphragm guide wall into several layers according to the depth of the surrounding soil;

[0069] In the early stage of deep foundation pit construction, excavation construction is carried out according to the guide wall levels, and displacement and settlement observations are carried out on different guide wall levels.

[0070] A group of pore water pressure gauges are arranged at the bottom of the diaphragm wall guide wall and the deep foundation pit, and a settlement detection point is set at the top of the diaphragm wall guide wall to arrange a total station to obtain the measured value of the settlement rate;

[0071] According to the initial detection cycle, the actual pore water pressure is detected, and the pore water pressure difference between the actual pore water pressure detected in the current initial detection cycle and the historical pore water pressure detected in the previous initial detection cycle is calculated.

[0072] Calculate the predicted settlement rate of the soil around the foundation pit and determine the ground settlement state. The predicted settlement rate = k × (du / dt) × e^(-αt);

[0073] Where du / dt is the pore pressure change rate, that is, the rate of change of pore water pressure within the initial detection period, k is the seepage sedimentation coefficient, α is the attenuation coefficient, t is the excavation time, and e is a constant;

[0074] In this example, k = 0.5 mm / (day·kPa) reflects the effect of soil permeability on settlement, α = 0.1 / day represents the degree of natural decay of settlement rate over time, and e^(-αt) is an exponential decay term that takes into account the effect of the gradual slowing of settlement rate during soil consolidation.

[0075] If the pore water pressure difference is less than the standard water pressure difference, and the predicted settlement rate is less than the standard settlement rate, the deep foundation pit is judged to be in the first settlement state, and the actual horizontal displacement of the diaphragm wall guide wall is detected;

[0076] If the pore water pressure difference is greater than or equal to the standard water pressure difference, or the predicted settlement rate is greater than or equal to the standard settlement rate, the deep foundation pit is judged to be in the second settlement state and the ground settlement state continues to be monitored;

[0077] Wherein, the standard water pressure difference is 10kPa, and the standard sedimentation rate is 2mm / d.

[0078] The predicted sedimentation rate is compared with the measured value of the sedimentation rate. When the predicted sedimentation rate is more than 30% smaller than the measured value, the seepage sedimentation coefficient k is corrected. The corrected seepage sedimentation coefficient k = original k × (measured value / predicted sedimentation rate).

[0079] Specifically, ground settlement is related to retaining wall deformation and pore water pressure. It is inaccurate to judge the foundation pit settlement by only using a single data point, the pore water pressure difference, as the pore water pressure is affected by the groundwater level distribution and other factors. At the same time, due to the long settlement observation period, this method predicts the foundation pit settlement rate through soil sensitivity, water pressure drop rate, and time attenuation effect. The pore water pressure difference and the predicted settlement rate reflect whether the settlement state of the deep foundation pit is stable, and different treatment measures are taken accordingly to improve the stability of the deformation trend prediction of the deep foundation pit.

[0080] When the deep foundation pit is in the first settlement state, the actual horizontal displacement of the ground-connected wall guide wall before the internal support is removed is measured using inclinometers buried at different depths.

[0081] During implementation, the inclinometer's inclinometer tube was tied to the ground-connected wall reinforcement cage and cast simultaneously with the wall to ensure coordinated deformation with the wall.

[0082] The actual horizontal displacement is equal to the measured horizontal displacement - concrete thermal expansion coefficient × temperature difference × measuring section length. The concrete thermal expansion coefficient in the implementation is 12 × 10 -6 / ℃;

[0083] The temperature difference is the difference between the ground-connected wall temperature detected by the temperature sensor and the preset temperature, the preset temperature is the measured temperature after the concrete solidifies, and the measuring section length is the excavation depth at the measuring point;

[0084] Draw the displacement curve of the ground-connected wall. The horizontal axis of the curve is the horizontal displacement, the positive direction of the horizontal axis is the inside of the foundation pit, and the vertical axis of the curve is the depth.

[0085] The displacement curve is divided into the wall top area, the excavation surface area and the wall bottom area according to the excavation depth, and the horizontal displacement of the displacement curve in the corresponding area is obtained;

[0086] If all horizontal displacements in the corresponding area meet the curve diagnosis conditions, the internal support is judged to be normal, and the total horizontal displacement of the diaphragm wall and guide wall after the support is removed is estimated;

[0087] If any horizontal displacement in the corresponding area does not meet the curve diagnosis conditions, it is judged that the internal support of the corresponding area is loose, and the load acting on the internal support of the corresponding area is checked.

[0088] Specifically, the judgment situation of not meeting the curve diagnosis condition is:

[0089] If the horizontal displacement of the wall top is greater than 0.2% of the excavation depth, the support system is judged to have failed and the wall top area does not meet the curve diagnosis conditions;

[0090] If the maximum displacement of the excavation surface is greater than 0.15% of the excavation depth, the wall bending moment is judged to be excessive and the excavation surface area does not meet the curve diagnosis conditions;

[0091] If the wall bottom displacement increment is greater than the standard displacement for three consecutive days, it is judged that the base is uplifted and the wall bottom area does not meet the curve diagnosis conditions;

[0092] Wherein, the standard displacement is 2 mm.

[0093] It is understandable that the implementers may divide the wall top area, the excavation surface area and the wall bottom area according to the excavation depth, which will not be described in detail here.

[0094] Specifically, due to the thermal expansion characteristics of the concrete constituting the guide wall of the ground-connected wall, the horizontal displacement of the guide wall at different depths is affected by temperature. After detecting the horizontal displacement, this method eliminates the influence of the thermal expansion of concrete on the measured value of the horizontal displacement of the guide wall of the ground-connected wall by calculating the actual horizontal displacement, thereby improving the measurement accuracy of the horizontal displacement of the guide wall of the ground-connected wall; and according to the displacement characteristics of the guide wall, corresponding evaluation criteria are set in different areas of the guide wall, and the displacement curve is diagnosed by the evaluation of the horizontal displacement in the corresponding area to judge whether it meets the curve diagnosis conditions and determine the support situation of the internal support. According to the support situation of the internal support, it is decided to estimate the horizontal displacement of the guide wall of the ground-connected wall after the support is removed or to check the acting load of the internal support in the corresponding area, thereby improving the adaptability and flexibility of deformation trend prediction for deep foundation pits.

[0095] Stress gauges and axial force gauges are installed at different depths on the inner and outer sides of the guide wall of the ground-connected wall to detect the loads acting on the ground-connected wall at different depths and the loads acting on several internal supports;

[0096] The load Fn of the internal support is detected by the axial force meter, and the load Fb of the ground-connected wall is detected by the concrete stress meter. The load loss Fs generated in the conversion process between the two is calculated.

[0097] During the internal support removal stage, the load loss Fs = β(Fn-Fb), where β is the conversion coefficient. Its magnitude is related to factors such as the time and method of internal support removal and the strength of the structural slab after removal.

[0098] Before the internal support removal stage, if the load loss Fs is greater than 30% of the applied load Fn, it is judged that the reason why the horizontal displacement does not meet the curve diagnosis conditions is the internal support load loss, and compensation measures are taken for the internal support;

[0099] Specifically, the compensation measure is to use a jack to re-jack up or temporarily add spare supports.

[0100] Specifically, due to reasons such as installation gap loss, deformation coordination loss, prestress relaxation and temperature reduction, the load acting on the inner support applied to the guide wall of the ground-connected wall has load loss. When the load loss exceeds the preset allowable loss rate, this method determines that the reason why the horizontal displacement does not meet the curve diagnosis conditions is the internal support load loss. Compensation measures are adopted for the internal support to prevent the internal support from being unable to provide load support to the guide wall of the ground-connected wall normally due to load loss, resulting in continuous horizontal displacement of the guide wall, causing deformation of the deep foundation pit or aggravating the deformation trend of the deep foundation pit, thereby affecting the accuracy of subsequent prediction of the deformation trend of the deep foundation pit.

[0101] When the deep foundation pit is in the first settlement state and the horizontal displacements in the corresponding area all meet the curve diagnosis conditions, estimate the total horizontal displacement of the diaphragm guide wall at several guide wall levels after the support is removed;

[0102] The initial displacement is the detection value, and the displacement increment after the support is removed = Pb 2 (3a+2b) / 6WI, where δ is the horizontal displacement increment, W is the elastic modulus of the guide wall of the ground-connected wall, I is the moment of inertia of the internal support, P is the detected support axial force, and a and b are the level lengths of different guide wall levels;

[0103] The total horizontal displacement is equal to the sum of the displacement increment after the support is removed and the initial displacement before the support is removed. The deformation evaluation value E is calculated based on the estimated total horizontal displacement and the current excavation depth;

[0104] ( +η·ln(h)),

[0105] Where, is the soil parameter, η is the construction influence coefficient, δ is the measured horizontal displacement value, and h is the current excavation depth;

[0106] The value range is 0.8~1.0, and the value range of η is 0.1~0.15. In this embodiment, Take 1.0 and η take 0.1.

[0107] If the deformation evaluation value is less than or equal to the first-level evaluation value, the deformation trend of the foundation pit is judged to be normal, and conventional construction is carried out to remove the internal support in a bottom-up manner;

[0108] If the deformation evaluation value is greater than the first-level evaluation value and less than the second-level evaluation value, it is judged that there is a risk in the deformation trend of the foundation pit, and the initial detection period is shortened and the internal support removal steps are adjusted;

[0109] If the deformation evaluation value is greater than or equal to the secondary evaluation value, it is judged that the deformation trend of the foundation pit exceeds the safety range and construction is stopped;

[0110] Among them, the first-level evaluation value is 0.3, and the second-level evaluation value is 0.6.

[0111] Specifically, before the internal supports of the deep foundation pit are removed, the deep foundation pit is in the first settlement state and the horizontal displacements in the corresponding areas all meet the curve diagnosis conditions. The method estimates the total horizontal displacement of the ground-connected wall and the guide wall after the internal supports are removed, thereby eliminating influencing factors and increasing the accuracy of the estimation of the total horizontal displacement; the deformation evaluation value of the deep foundation pit is calculated according to the total horizontal displacement and the current depth, and through real-time monitoring and calculation of the deformation evaluation value, the deformation trend of the foundation pit is discovered in time, and corresponding measures are taken to avoid instability of the foundation pit or damage to surrounding buildings due to excessive deformation. This method provides a scientific and effective deformation assessment method for deep foundation pit construction, which helps to improve construction safety, optimize construction progress, reduce construction costs, improve construction efficiency, and ensure the safety of the surrounding environment.

[0112] Remove the internal supports at different guide wall levels according to the determined support removal sequence, detect the actual horizontal displacement of the diaphragm guide wall after removing the internal supports at the current guide wall level in real time, and compare the estimated total horizontal displacement with the actual horizontal displacement detected;

[0113] If the difference between the estimated total horizontal displacement of the current support removal layer and the actual horizontal displacement detected is less than the difference evaluation value, the estimated result is judged to be within the normal range, and the support removal is continued according to the determined support removal order;

[0114] If the difference between the estimated total horizontal displacement of the current support removal layer and the actual detected horizontal displacement is greater than or equal to the difference evaluation value, the estimated result is judged to be out of the normal range, and the displacement increment after support removal is adjusted at the guide wall level where the inner support in the next support removal sequence is located;

[0115] Specifically, when the estimated total horizontal displacement is smaller or larger than the actually detected horizontal displacement, the displacement increment predicted for the guide wall level of the inner support in the next support removal sequence after support removal is reduced or increased according to the ratio of the displacement difference to the difference evaluation value;

[0116] The difference evaluation value is 2% of the total horizontal displacement.

[0117] Specifically, during the calculation process, the guide wall of the ground-connected wall is simplified to a vertically placed beam. However, in reality, the width of the guide wall of the ground-connected wall is relatively large, so there is a certain difference between the estimated total horizontal displacement calculated theoretically and the actual measured value. This method compares the estimated total horizontal displacement with the actual horizontal displacement detected, and adjusts the displacement increment after the removal of the inner support at the guide wall level in the next support removal sequence according to the comparison result. This improves the estimation accuracy of the estimated total horizontal displacement at different guide wall levels in the deep foundation pit deformation trend prediction, and avoids the deformation of the guide wall causing ground displacement or affecting the safety of the foundation pit construction.

[0118] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

[0119] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for predicting deformation trends of deep foundation pits based on multimodal sensing data, characterized in that: include: Detect the actual pore water pressure according to the initial detection cycle, and determine the formation settlement state based on the calculated pore water pressure difference and the predicted settlement rate; Determining to continue monitoring the ground settlement state or detecting the actual horizontal displacement of the diaphragm wall guide wall according to the ground settlement state, calculating the actual horizontal displacement based on the measured horizontal displacement, and drawing a displacement curve of the diaphragm wall guide wall; Determine the support condition of the internal support according to the curve diagnosis condition of the displacement curve, estimate the total horizontal displacement of the diaphragm wall guide wall at several guide wall levels after the support is removed, or check the load acting on the internal support in the corresponding area; Check the loads acting on the internal supports and ground-connected walls to calculate the load loss and determine whether the reason why the horizontal displacement does not meet the curve diagnosis conditions is due to internal support load loss; Calculate the total horizontal displacement of the diaphragm guide wall at several guide wall levels after the support is removed based on the estimated displacement increment after support removal, calculate the deformation evaluation value based on the total horizontal displacement and the current excavation depth, and determine the foundation pit deformation trend and support removal sequence; Remove the internal supports at different guide wall levels according to the determined support removal sequence, and adjust the displacement increment of the next guide wall level based on the comparison result between the estimated total horizontal displacement and the actual horizontal displacement detected; The guide wall level is a level division of the ground-connected wall guide wall according to the depth of the surrounding soil where the ground-connected wall guide wall is located; The process of determining the subsidence state of the formation includes, Detect the actual pore water pressure according to the initial detection cycle, calculate the pore water pressure difference between the actual pore water pressure detected in the current initial detection cycle and the historical pore water pressure detected in the previous initial detection cycle, and calculate the predicted settlement rate of the soil around the foundation pit; If the pore water pressure difference is less than the standard water pressure difference, and the predicted settlement rate is less than the standard settlement rate, the deep foundation pit is judged to be in the first settlement state, and the actual horizontal displacement of the diaphragm wall guide wall is detected; If the pore water pressure difference is greater than or equal to the standard water pressure difference, or the predicted settlement rate is greater than or equal to the standard settlement rate, the deep foundation pit is judged to be in the second settlement state and the ground settlement state continues to be monitored; The process of drawing the displacement curve of the guide wall of the ground-connected wall includes: The actual horizontal displacement is calculated based on the measured horizontal displacement, temperature difference, and measurement section length, and the displacement curve of the ground-connected wall guide wall is drawn. The displacement curve is divided into the wall top area, the excavation surface area, and the wall bottom area, and the horizontal displacement of the displacement curve in the corresponding area is obtained; If all horizontal displacements in the corresponding area meet the curve diagnosis conditions, the internal support is judged to be normal, and the total horizontal displacement of the diaphragm wall and guide wall after the support is removed is estimated; If any horizontal displacement in the corresponding area does not meet the curve diagnosis conditions, it is judged that the internal support of the corresponding area is loose, and the load acting on the internal support of the corresponding area is checked.

2. The method for predicting deformation trend of deep foundation pit based on multimodal sensing data according to claim 1, characterized in that: The judgment situation that does not meet the curve diagnosis conditions is: If the horizontal displacement of the wall top is greater than 0.2% of the excavation depth, the support system is judged to have failed and the wall top area does not meet the curve diagnosis conditions; If the maximum displacement of the excavation surface is greater than 0.15% of the excavation depth, the wall bending moment is judged to be excessive and the excavation surface area does not meet the curve diagnosis conditions; If the wall bottom displacement increment is greater than the standard displacement for three consecutive days, it is judged that the base is uplifted and the wall bottom area does not meet the curve diagnosis conditions.

3. The method for predicting deformation trend of deep foundation pit based on multimodal sensing data according to claim 2, characterized in that: The process of checking the load acting on the internal supports of the corresponding area includes, The load acting on the internal support is detected by an axial force meter, and the load acting on the guide wall of the ground-connected wall is detected by a concrete stress meter, and the load loss generated during the conversion process between the two is calculated; Before the internal support removal stage, if the load loss is greater than 30% of the applied load, it is judged that the reason why the horizontal displacement does not meet the curve diagnosis conditions is the loss of internal support load, and compensation measures are taken for the internal support.

4. The method for predicting deformation trend of deep foundation pit based on multimodal sensing data according to claim 2, characterized in that: The process of estimating the total horizontal displacement of the diaphragm guide wall after the support is removed includes: The displacement increment after the support is removed is estimated, and the total horizontal displacement is equal to the sum of the displacement increment after the support is removed and the initial displacement before the support is removed. The deformation evaluation value is calculated based on the estimated total horizontal displacement and the current excavation depth.

5. The method for predicting deformation trend of deep foundation pit based on multimodal sensing data according to claim 4 is characterized in that: When the deformation evaluation value is less than or equal to the first-level evaluation value, the deformation trend of the foundation pit is judged to be normal; When the deformation evaluation value is greater than the first-level evaluation value and less than the second-level evaluation value, it is judged that there is a risk in the deformation trend of the foundation pit; When the deformation evaluation value is greater than or equal to the secondary evaluation value, it is judged that the deformation trend of the foundation pit exceeds the safety range.

6. The method for predicting deformation trend of deep foundation pit based on multimodal sensing data according to claim 5, characterized in that: When the deformation trend of the foundation pit is normal, carry out routine construction and remove the internal supports in a bottom-up manner; When there is a risk of foundation pit deformation, shorten the initial inspection period and adjust the internal support removal steps; Stop construction when the deformation trend of the foundation pit exceeds the safe range.

7. The method for predicting deformation trend of deep foundation pit based on multimodal sensing data according to claim 6, characterized in that: Remove the internal supports at different guide wall levels according to the determined support removal sequence, detect the actual horizontal displacement of the diaphragm guide wall after removing the internal supports at the current guide wall level in real time, and compare the estimated total horizontal displacement with the actual horizontal displacement detected; If the difference between the estimated total horizontal displacement of the current support removal layer and the actual horizontal displacement detected is less than the difference evaluation value, the estimated result is judged to be within the normal range, and the support removal is continued according to the determined support removal order; If the difference between the estimated total horizontal displacement of the current support removal layer and the actual detected horizontal displacement is greater than or equal to the difference evaluation value, the estimated result is judged to be out of the normal range, and the predicted displacement increment of the guide wall layer in the next support removal sequence is adjusted.

8. The method for predicting deformation trend of deep foundation pit based on multimodal sensing data according to claim 7, characterized in that: The process of adjusting the displacement increment includes, When the estimated total horizontal displacement is less than or greater than the actual detected horizontal displacement, the displacement increment predicted after the support removal at the guide wall level of the internal support in the next support removal sequence is reduced or increased according to the ratio of the displacement difference and the difference evaluation value.

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